1. Field of the Invention
This invention relates to a spacecraft panel (panel with a built-in heat pipe for a spacecraft), and this invention relates to a heat pipe placed to form a grid in the panel with the built-in heat pipe for the spacecraft.
2. Description of the Related Art
FIG. 37 illustrates the spacecraft panel according to the related art.
In the spacecraft panel (panel with the built-in heat pipe for the spacecraft), a two-layer heat pipe layout is adopted. A heat pipe (called “lateral heat pipe” hereinafter) in a side facing a plane in which a device is installed and a heat pipe (called “header heat pipe” hereinafter) in a side facing a heat radiation plane are placed in orthogonal positions each other and thermally coupled. Accordingly, heat radiation efficiency is improved, and heat is exchanged.
Particularly, at a crossing part of the lateral heat pipe and the header heat pipe, a thermal joint structure is adopted for expediting thermal exchange between the lateral heat pipe and the header heat pipe. In the thermal joint structure, a fin is provided in the header heat pipe, and the lateral heat pipe and the header heat pipe are coupled thermally. The fin is provided only in the header heat pipe as it is easier to process the header heat pipe which is less than the lateral heat pipe. Further, unlike the lateral heat pipe in which a pitch is almost fixed depending on a size of the installed device, constraint in packaging, fin efficiency of a whole panel, and a structure insert position, the header heat pipe can be positioned flexibly.
FIG. 38 illustrates a joint part of a cut model of a header heat pipe of single type and a cut model of a lateral heat pipe according to the related art.
In the following explanation, the “cut model of the header heat pipe” is called “header heat pipe,” and the “cut model of the lateral heat pipe” is called “lateral heat pipe.”
In FIG. 38, a lateral heat pipe 10, a flat part 11, a header heat pipe 20, a flat part 21, and a fin 25 are illustrated.
FIG. 39 illustrates the header heat pipe of single type according to the related art. In FIG. 39, a pipe part 24 is illustrated.
FIG. 40 illustrates the lateral heat pipe of single type according to the related art. In FIG. 40, a pipe part 14 is illustrated.
FIG. 41 illustrates a header heat pipe of dual type according to the related art.
The flat part 21, the fin 25 and the pipe part 24 in FIG. 41 are same as those in FIG. 39. In FIG. 41, an adjacent direction 22 of the pipe part 24 is illustrated. In FIG. 41, a symmetry line 23 and a header heat pipe 200 are illustrated. In the header heat pipe 200, elements are placed symmetrically with respect to the symmetry line 23.
The fin 25 is provided in both sides of the header heat pipe 20 for increasing a heat transfer area. However, since a plurality of pipe parts 24 are adjacent in the header heat pipe 200, each of the pipe parts 24 can use the fin 25 only in one side for heat transfer. Therefore, the heat transfer area of each of fins for the header heat pipe 200 of dual type must be wider than that for the header heat pipe 20 of single type. As a result, a weight of the header heat pipe 200 becomes heavier.
FIG. 42 illustrates the header heat pipe of dual type according to the related art.
The flat part 21, the fin 25 and the pipe part 24 in FIG. 42 are same as those in FIG. 39. In FIG. 42, the adjacent direction 22 of the pipe parts 24 is illustrated. In FIG. 42, the header heat pipe 200, a concave part 17, the symmetry line 23 and an uneven part 29 are illustrated. In the header heat pipe 200, elements are placed symmetrically with respect to the symmetry line 23.
FIG. 43 illustrates a lateral heat pipe of dual type according to the related art.
The flat part 11 and the pipe part 14 in FIG. 43 are same as those in FIG. 40. In FIG. 43, an adjacent direction 12 of the pipe part 14 is illustrated. In FIG. 43, a lateral heat pipe 100 of dual type, a symmetry line 13 and the concave part 17 are illustrated. In the lateral heat pipe 100, elements are placed symmetrically with respect to the symmetry line 13.
Each of the header heat pipes 20 and 200 and the lateral heat pipes 10 and 100 is made of aluminum alloy and created by press-out processing.
In the press-out processing, a thickness of each parts must be almost equal for a purpose of processing. Otherwise, it is difficult to process a delicate inner shape of the pipe parts 14 and 24 of the heat pipe. In FIGS. 39, 40, 42 and 43, an outer shape of the pipe parts 14 and 24 is a circle similar to the inner shape of the pipe parts 14 and 24 or a polygon (octagon, for example) close to the circle.
A weight of the header heat pipe 200 in FIG. 42 is lighter than a weight of the header heat pipe 200 in FIG. 41 as the header heat pipe 200 in FIG. 42 has the concave part 17.
However, in the header heat pipe 200 in FIG. 42, the fin 25 is provided by combining the outer shape of the pipe part 24 which is the circle similar to the inner shape of the pipe part 24 or the polygon (octagon, for example) close to the circle and a shape of the fin 25 in a L shape. Therefore, the uneven part 29, i.e., groove, is created between the flat part 21, i.e., one of outer surfaces of the pipe part 24, and the fin 25 which are actual heat transfer planes. As a result, there is a problem that heat transfer efficiency is low.
In the lateral heat pipes 10 and 100, the flat part 11, i.e., actual heat transfer plane, is one of the outer surfaces of the pipe part 24 and a side of the polygon (octagon, for example).
Like the header heat pipe 200 in FIG. 42, a weight of the lateral heat pipe 100 in FIG. 43 is lighter than a weight of the lateral heat pipe without the concave part 17. However, because of the concave part 17 provided, there is a problem that the heat transfer efficiency is low.
In designing a shape of the heat pipe for the spacecraft, there are problems concerning on the heat and the weight as following (1) and (2):
(1) For reducing a weight of a spacecraft structure, it is necessary to reduce a weight of a heat pipe structure which is a main weight component of a panel by optimizing a shape of the heat pipe structure; and
(2) At the same time, it is becoming impossible to ignore a temperature drop at a heat pipe joint part as a device installed in the spacecraft has come to emit heat at a high temperature. Therefore, it is necessary to set guidelines on designing of the heat pipe for reducing the weight without causing a temperature drop.
About problem (1), it is most efficient to reduce a thickness of a pipe material of the heat pipe which is a pressure container by cutting an unnecessary thickness. However, it is impossible to solve the problem (2) concerning on the heat only by reducing the thickness. Hence, competitiveness as products becomes lower in a market as it is necessary to cope with a device of which temperature gets higher and improve the radiation efficiency. For designing a high performance heat pipe panel, it is necessary to set guidelines on a sectional shape and a joint structure with a good total balance of the heat and the weight.